César Viho

Using On-The-Fly Verification Techniques for the Generation of test Suites

In this paper we attempt to demonstrate that on-the-fly techniques, developed in the context of verification, can help in deriving test suites. Test purposes are used in practice to select test cases according to some properties of the specification. We define a consistency pre-order linking test purposes and specifications. We give a set of rules to check this consistency and to derive a complete test case with preamble, postamble, verdicts and timers. The algorithm, which implements the construction rules, is based on a depth first traversal of a synchronous product between the test purpose and the specification. We shortly relate our experience on an industrial protocol with TGV, a first prototype of the algorithm implemented as a component of the C ADP toolbox.

An experiment in automatic generation of test suites for protocols with verification technology

Abstract In this paper we describe an experiment in automatic generation of test suites for protocol testing. We report the results gained with generation of test suites based on advanced verification techniques applied to a real industrial protocol. In this experiment, several tools have been used: the commercial tool GEODE (VERILOG) was used for the generation of finite state graph models from SDL specifications, the tool Aldebaran of the CADP toolbox for the minimization of transition systems, and a prototype named TGV (for Test Generation using Verification techniques) for the generation of test suites which has been developed in the CADP toolbox. TGV is based on verification techniques such as synchronous product and on-the-fly verification. These tools have been applied to an industrial protocol, the DREX protocol. The comparison of produced test suites with hand written test suites proves the relevance of the used techniques.

Quality of Experience Measurements for Video Streaming over Wireless Networks

As wireless networks have been increasingly deployed, the need of quality measurement became essential since network operators want to control their network resources while maintaining user satisfaction. More importantly, measurement of technical parameters fails to give an account of the user experience, what could be named QoE (Quality of Experience). Therefore, many techniques have been developed in order to assess as accurately as possible this perceptual quality. To investigate QoE measurement, this paper presents three approaches namely subjective approach, objective approach, and hybrid approach. It also presents performance evaluation of these approaches for assessing QoE in video streaming application over wireless networks in different network conditions (using variation of loss rate and its distribution). We focus more specifically on a hybrid approach called Pseudo Subjective Quality Assessment (PSQA) that keeps advantages of both subjective and objective schemes while minimizing their drawbacks. We demonstrate that this approach provides good estimations comparing to the well-known objective metric called Peak Signal to Noise Ratio (PSNR). We also observe that PSQA gives similar result comparing to subjective test that has been evaluated by human observers in most of the cases. Moreover, one objective of this evaluation is to validate PSQA for QoE measurement, which will facilitate the use of QoE as metric for resource management in the future. For that, we also give some possible directions allowing us to manage network resources using this metric.

Radio resource management in emerging heterogeneous wireless networks

Deployment of heterogeneous wireless networks is spreading throughout the world as users want to be connected anytime, anywhere, and anyhow. Meanwhile, these users are increasingly interested in multimedia applications such as video streaming and Voice over IP (VoIP), which require strict Quality of Service (QoS) support. Provisioning network resources with such constraints is a challenging task. In fact, considering the availability of various access technologies (WiFi, WiMAX, or cellular networks), it is difficult for a network operator to find reliable criteria to select the best network that ensures user satisfaction while maximizing network utilization. Designing an efficient Radio Resource Management (RRM), in this type of environment, is mandatory for solving such problems. In order to provide a better understanding of RRMs design, this paper presents a detailed investigation of key challenges that constitute an efficient RRM framework. More importantly, an overview with a classification of recent solutions, in terms of decision making, is provided along with the discussion.

QoE-Aware Admission Control for Multimedia Applications in IEEE 802.11 Wireless Networks

Widespread use of wireless networks nowadays raises many problems for service providers in managing their resources. These problems are caused mainly by restricted bandwidth and variable radio condition in this type of network. Moreover, with the emergence of multimedia traffic and its requirements in terms of quality, admission control is hence an inevitable choice to optimize network resources while maintaining high service quality at users. In this paper, we propose an admission control mechanism based on quality of experience (QoE) perceived by users. The human QoE is obtained by a tool called pseudo subjective quality assessment (PSQA), which is based on statistic learning using random neural network (RNN). Instead of relying on technical parameters such as bandwidth, loss, or latency, which do not correlate well with human perception, our scheme is based on mean opinion score (MOS) but without interaction from real humans. The simulation results demonstrate the better performance of our proposition compared to the loss-based approach regarding user satisfaction evaluated by achieved QoE at user and bandwidth utilization of the network evaluated by good put.

Remote testin can be as powerful as local testing

Designing test cases for remote asynchronous testing is error-prone. This is due to the difficulty to foresee all the disorders on the observations collected by the tester as well as the possible collisions between stimuli and observations. Designing correct synchronous test cases is easier, but transforming,them into correct asynchronous ones is a difficult task. Moreover, it is difficult to compare remote testing and local testing as in general sets of conformant implementations are not comparable.

Towards Automatic Distribution of Testers for Distributed Conformance Testing

This paper presents first steps towards automatic generation of distributed tests. We first define a characterization of the tests for which the property of unbias is preserved by the existence of an asynchronous environment. Then, starting from a centralized test case, we propose a method to derive automatically its corresponding distributed test case in an asynchronous environment. We prove that the generated distributed test case is not biased, it tests the same behaviors of an implementation and has the same testing power as the centralized test case.

QoE-based network selection for multimedia users in IEEE 802.11 wireless networks

Widespread use of wireless networks nowadays raises many challenging issues to be explored. With increasing of multimedia traffic, quality of experience (QoE) needs to be satisfied at users while overall performance needs to be maintained at networks. In order to achieve these goals, the use of network selection mechanism is inevitable. When several access points are present, user should select the best available network while trying to keep load balanced between access networks. In this paper, we present a user-based and network-assisted scheme for network selection in wireless IEEE 802.11 technology. By providing users in decision making process with relevant information about the networks, the proposed solution keeps compromising advantage for both user and network. Our mechanism is based on a technique called pseudo-subjective quality assessment (PSQA), which is used basically to measure quality of experience perceived by users. We propose a new scheme where PSQA tool is used to assist in terminal-centric network selection. We explain the scheme and illustrate its efficient performance compared to a signal-based mechanism.

An Industrial Experiment in Automatic Generation of Executable Test Suites for a Cache Coherency Protocol

In this paper, we present an end-to-end industrial case-study concerning the automatic generation of tests suites for the Cache Coherency Protocol of a Multiprocessor Architecture. It consists of the following stages: (1) formal specification of the architecture using Lotos language, (2) formal description of the test purposes, (3) automatic generation of abstract test suites using the prototype TGV, and (4) automatic generation and analysis of executable test suites. Through the description of each of the previous stages, this paper demonstrates that tools designed for protocol conformance testing can be efficiently used to generate executable tests for hardware concurrent systems.

System Design of a CC-NUMA Multiprocessor Architecture Using Formal Specification, Model-Checking, Co-Simulation, and Test Generation

Abstract.The application of formal methods to the system-level design of hardware components is still an open issue for which concrete case-studies are needed. We present here an industrial experiment concerning the application of the process algebraic language lotos (iso standard 8807) to the design of polykid, a cc-numa (cache coherent – non-uniform memory access ) multiprocessor architecture developed by bull. The formal descriptions developed for polykid have served as a basis not only for model-checking verification using cadp (caesar/aldebaran development package), but also for hardware-software co-simulation using the exec/caesartool, and for automatic generation of executable tests using the tgv tool.